1. Field of the Invention
The present invention relates to a method of manufacturing an electronic device such as a semiconductor integrated circuit, a super conductive device, a micro-machine, TFT, or a printed wiring board. In particular, the invention relates to a technique effectively applicable to lithography in the manufacturing process of the semiconductor integrated circuit device.
2. Description of Related Art
In the production of semiconductor integrated circuit devices, lithography is used for transferring a fine pattern on a semiconductor wafer. In the lithography, a projection and exposure system is used and a device pattern is formed by transferring a pattern of a photomask mounted on the projection and exposure system to the semiconductor wafer.
A usual photomask is prepared by fabricating a shade material, such as chromium (Cr) formed on a transparent quartz glass substrate. That is, a shade film made of chromium or the like is formed in a desired shape on a quartz substrate. The shade film is fabricated, for example, as described below. That is, after coating an electron beam sensitive resist on a shade film, a desired pattern is delineated on the electron beam sensitive resist by an electron beam exposure system. Successively, after delineating a resist pattern of a desired shape by development, the shade film is fabricated by dry etching or wet etching using the resist pattern as a mask. Subsequently, after removing the resist, cleaning is conducted to form an opaque pattern of a desired shape on the quartz glass substrate.
In recent years, with an aim of improving the resolution of lithography, various mask structures have been proposed in addition to usual photomasks in which the shade film comprises a chromium or the like in a desired shape as described above. For example, in JP-A-136854/1992, the shade film of the photomask is made semi-transparent and the phase of slight light transmitting the semi-transparent area is inverted to transmit the transparent pattern. That is, the light at a level lower than the sensitivity of a photoresist for transferring the pattern is transmitted through the semi-transparent film and the phase of the light transmitting through the transparent pattern is inverted. Since the phase of the light transmitting via the semi-transparent film is inverted relative to the light transmitting the transparent pattern as a main pattern, the phase is inverted at the boundary and the intensity of light at the boundary approaches zero. Thus, the ratio between the intensity of light passing the transparent pattern and the intensity of light at the boundary of the pattern is relatively increased to obtain a distribution of light intensity with higher contrast compared with the technique not using the semi-transparent film. This is referred to as a half tone type phase shift mask. In the manufacture of the half tone phase shift mask, the shade film of the usual photomask is changed to a half tone phase shift film, which is manufactured substantially in the same step as the manufacturing step for the usual photomask.
Further, there is an exposure method referred to as resolution enhancement which provides patterning resolution much smaller than the exposure wavelength. Among the resolution enhancement processes, a Levenson-type phase shifting exposure process is most effective for forming a fine pattern. In the Levenson-type phase shifting exposure process, a structure called as a phase shifter for inverting the phase of the irradiation light is formed alternately in the irradiation light transmitting area, i.e., in the window where the glass surface is exposed of a usual photomask while the shade are putted therebetween is exposed by using the photomask. Since phase of lights transmitting both of the transmitting areas is inverted, a region where the amplitude of light is reduced to zero is formed in the sandwiched shade area. When the amplitude is zero, the intensity of light is also reduced to zero, and the resolution is improved significantly by about xc2xd of the exposure wavelength for the alternately arranged shade area (thinner than the window) and the phase shifter area. The photomask having such a shade area and a phase shifter area is referred to as a Levenson-type phase shift mask.
Due to increasing accuracy and versatile arrangements of semiconductor integrated circuit devices, the fabrication accuracy for the photomask used in the lithography also in the usual photomask becomes more stringent. Therefore, a phase shift mask having the special structure as described above becomes necessary. Accordingly, the production cost for such photomasks of about 20 to 40 plates are much more expensive, and the time required for the manufacture of the photomask becomes longer.
On the other hand, JP-A-289307/1993 discloses a method for forming a shade film in the photomask with a resist film instead of existent metal films such as of Cr. This method utilizes benzene (rings) as the main constituent element in a usual electron beam resist or photosensitive resist compositions because that they have an extremely large light absorption band at a wavelength of an ArF excimer laser beam source (about 193 nm). The etching step for the shade film or the resist removing step is not necessary according to this method, which reduces the cost, improves the dimensional accuracy, and reduces the defects of the photomask. In many existent high performance resists used in the KrF excimer laser lithography or electron beam lithography, phenolic polymer resins or derivatives thereof are used for the base polymer matrix providing the coatability. An aromatic ring (benzene ring) structure in such resins has an extremely large absorption maximum near the wavelength of the ArF excimer laser beam, and the transmittance at the wavelength of 193 nm is 1% or less with a film thickness only of 0.1 xcexcm in such a resin coating layer. Accordingly, in the resist material using the resin described above as the matrix, the transmittance to the ArF excimer laser beam is 0.01% or less even at the film thickness of about 0.3 xcexcm which is used frequently, which provides a substantially ideal shade film. However, the transmittance of such resin increases near the wavelength of the existent KrF excimer laser beam (about 248 nm) and the transmittance is 30% or more even at the film thickness for forming a fine pattern (usually about 0.3 to 1.0 xcexcm). Accordingly, such a resist can not be used for the shade film of the photomask in KrF excimer laser lithography.
The technique described above for forming the shade film in the photomask with a resist film of large light absorption at the exposure wavelength (instead of an existent metal film such as made of Cr) creates problems, and countermeasures therefor in the prior art to the photomask for the existent KrF excimer lithography are not disclosed. The subject of this invention is to provide a photomask for KrF excimer laser lithography using an opaque pattern that utilizes the light absorption characteristic of the organic resin composition, and to provide a method applying such a mask to produce semiconductor devices. The KrF excimer laser lithography is an exposure method used in a volume zone of semiconductor devices, and producing semiconductor devices by the KrF excimer laser lithography with such a mask reduces cost, and provides a high accuracy and less defect density.
In various existent kinds of high performance resists, the transmittance is 30% or more near the wavelength of the KrF excimer laser beam (about 248 nm) at a film thickness for forming a fine pattern (usually about 0.3 to 1.0 xcexcm). Accordingly, the resists described above can not be used as they are for the shade film of the photomask for KrF excimer laser lithography. An obvious countermeasure is to incorporate a compound or a chemical structure having an absorption band in a wavelength region of a KrF excimer laser beam into an existent resist composition of high resolution. However, a light absorption compound that can be incorporated in the composition without greatly deteriorating the resolution performance or the like was not yet known. It is a subject of this invention to provide a resist composition that enables a resist pattern to be formed directly on a quartz glass substrate as a photomask (a shade film) for KrF excimer laser lithography, as well as to manufacture a photomask for KrF excimer laser lithography with the resist composition.
Further, in the prior art, a resist pattern of extremely low transmittance substantially equivalent with a metal shade film, such as made of Cr, can be used as a shade film but not as a half tone film. That is, it is also a subject of this invention to provide a method of using a resist pattern formed directly on a quartz glass substrate as an attenuator to the phase shift mask, such as a half tone type phase shift mask, in the KrF excimer laser lithography.
The shade film with light absorption characteristic made of the organic resin composition suffers a greater restriction of durability, such as light stability, in comparison with a shade film comprising metal film, such as of Cr, in a usual photomask. The prior art provides a method for improving the durability by the heat treatment after the formation of the pattern. The present inventors have studied the light stability of an organic resin composition shade film utilizing the light absorption characteristic in the KrF excimer laser exposure system and found that the organic polymer layer having a light absorption band at an exposure wavelength inevitably suffer from change due to any photochemical reaction in an exposure environment for a long period of time. Accordingly, a new subject of this invention is to provide a method of effectively using a photomask having an organic resin composition shade film without suffering from the change of photochemical reaction and, particularly, a method of effectively using the mask to produce semiconductor integrated circuit devices.
This invention provides a photomask for KrF excimer laser lithography using an opaque pattern that utilizes the light absorbing characteristic of an organic resin composition so as to apply the photomask effectively to produce semiconductor devices.
A. It has been found that a light sensitive resin composition containing at least one of light absorption compounds represented by the following general formulae (1)-(8) can be used for the photosensitive polymer layer capable forming a resist pattern to be applied to a photomask for KrF excimer laser lithography instead of the opaque pattern comprising a metal film such as of Cr. xe2x80x9cContainingxe2x80x9d means herein that the compound is blended as one of ingredients of the composition, as well as it is chemically bonded previously to other composition. 
where R1 to R10 each represents an atom or atom group selected from the group consisting of hydrogen, a substituted or non-substituted alkyl group of 1 to 4 carbon atoms, a halogen, a hydroxy group, a methylol group, a substituted or non-substituted alkoxy group of 1 to 4 carbon atoms, a hydroxyl group, a phenyl group, a methoxy group, an ethoxyethyl group, a cyclopropyl group, an acetal group and an acetyl group. R1 to R10 may be identical to or different from one another. X represents a halogenated acetyl group, and Y represents an atom or an atom group selected from a group consisting of camphor sulfonate, trifluoro sulfonate and methane sulfonate.
More specifically, the compound may include, for example, anthracene, anthrarobin, benzoquinoline, phenantol, 1-methoxy-9,10-dibromoanthracene, 2-hydroxymethyl anthracene, 9-hydroxymethyl anthracene, 9-bromoanthracene, 9-chloromethyl anthracene, methoxymethyl anthracene, 1-amino anthracene, acetoxy anthracene, 2-bromoacetyl naphthalene, 2-bromoacetyl-6,7-dimethoxy naphthalene, 1-hydroxy-4-bromo-2-bromoacetyl naphthalene, 1,3,5-tris(bromoacetyl)benzene, 3-bromoacetyl cumarin and 3-bromomethyl-7-methoxy-1,4-benzoxadine-2-one.
The content of the light absorption compound in the composition and the film thickness are adjusted such that the transmittance of the thus formed opaque pattern to a KrF excimer laser beam is 1% or less, preferably 0.5% or less, and the composition is used as a photomask for KrF excimer laser lithography.
B. The photosensitive resin composition with the light absorption compound described above is applicable also to manufacture a half tone type phase shift mask for the KrF excimer laser lithography. The content of the light absorption compound in the composition and the film thickness are controlled such that the transmittance of the thus formed opaque pattern to a KrF excimer laser beam ranges from 2% to 16%, preferably 4% to 9%. The phase difference of the irradiation light transmitting the film to that of the transmission area is either xcfx80 or 3 xcfx80, and the composition is used as the half tone type phase shift mask for KrF excimer laser lithography.
C. The negative type photosensitive resin composition according to this invention, may be used as any known chemical amplification type negative resist compositions. A typical amplification type negative resist composition includes an aqueous alkali soluble resin, an acid catalyst crosslinker, and an acid generator. In the negative type photosensitive composition according to this invention, the light absorption compound shown in the above (1) is blended to the composition described above. Phenolic resins, such as novolak, resin and polyhydroxy styrene, as well as various phenolic compounds, can also be used as the organic alkali soluble resin so long as they can be dissolved in a solvent to form a film by spin coating. As the acid catalyst dissolution inhibition precursors (DIPs), hexamethoxy methyl melamine (HMMM) or the like crosslinkers are known. In addition, primary to tertiary alcohols having hydroxy groups on carbon atoms bonded directly to an aromatic ring can be used as DIPs. For example, m-xylene glycol, p-xylene glycol, 1,2,3-benzene tirmethanol, 2-hydroxy-5-methyl-1,3-benzene dimethanol, 3,5,3xe2x80x2,5xe2x80x2-hexahydroxymethyl-4,4-dihydroxydiphenyl, bis(3,5-dihydroxymethyl-4-hydroxyphenyl)methylene, 2,2-bis(3,5-dihydroxymethyl-4-hydroxyphenyl)propane, 1,4-bis(2-(3,5-dihydroxymethyl-4-hydroxyphenyl)propane)benzene, 1,3-bis(2-hydroxy-2-propyl)benzene, 1,3-bis(3-hydroxy-3-pentyl)benzene, 1,3-bis(2-hydroxy-2-propyl)-5-methoxybenzene, 5-chloro-1,3-bis(2-hydroxy-2-propyl)benzene, 5-bromo-1,3-bis(2-hydroxy-2-propyl)benzene, 1,4-bis(2-hydroxy-2-propyl)benzene, 1,4-bis(3-hydroxy-3-pentyl)benzene, 1,4-bis(2-hydroxy-2-propyl-2,3,5,6-tetramethyl)benzene, 2-chloro-1,4-bis(2-hydroxy-2-propyl)benzene, 2-bromo-1,4-bis(2-hydroxy-2-propyl)benzene, 1,3,5-tris(2-hydroxy-2-propyl)benzene, 1,3,5-tris(3-hydroxy-3-pentyl)benzene, 1,5-bis(2-hydroxy-2-propyl)naphthalene, 1,4-bis(2-hydroxy-2-propyl)naphthalene, or 9,10-bis(2-hydroxy-2-propyl)anthracene. The acid generator may include non-metal type onium salt (such as triphenyl sulfonium trifluoromethane sulfonate), diphenyl iodonium trifluoromethane sulfonate, and di-tert-butylphenyl iodonium methane sulfonate, sulfonate ester (such as p-toluene sulfonate-o-dinitrobenzyl, tris(methanesulfonyloxy) benzene), and tris(ethanesulfonyloxy)benzene and sulfonate imide (such as trifluoromethane sulfonate naphthylimide), and organic halogenide (such astris(2,3-dibromopropyl) isocyanurate).
D. The light absorption compound for providing the light sensitive resin composition according to this invention with a light absorption band can include those compounds described in the above (1). Particularly, anthracene derivative or phenanthrene derivative is more effective. This is because the molecular structure of anthracene or phenanthrene has a particularly large absorption band in a wavelength region of a KrF excimer laser beam.
E. Among all, for the negative type photosensitive resin composition described in the above (3), it is effective to use an anthracene derivative or a phenanthrene derivative having at least one carbinol group, for example, methylol group in the molecular structure. Most of the various kinds of high performance resists developed in recent years are so-called chemical amplification type resists which utilizes acid catalyst reaction for delineating patterns. Among all, in the negative type resist, it has been generally known to utilize an acid generated by pattern exposure from an acid generator in the composition as a catalyst in a crosslinking reaction. When an anthracene derivative or a phenanthrene derivative having the carbinol group is present in the negative type resin composition, the methylol structure at the carbinol terminal effectively bonds the anthracene derivative or the phenanthrene derivative to the matrix by the acid catalyst. This can prevent the light absorption in the process, such as coating or baking, from being lowered.
F. Among the photosensitive compositions according to this invention, a composition in which the transmittance of the opaque pattern to a KrF excimer laser beam is 1% or less, preferably 0.5% or less, is also used to form an opaque pattern in the Levenson-type phase shift mask.
G. In the projection exposure method for producing semiconductor integrated circuit devices, the photomask is exposed for a long period of time such that the organic resin opaque pattern having a light absorption band at the wavelength of the irradiation light inevitably suffers from change in the photochemical reaction. Then, for effectively using the photomask having the organic resin composition shade film to produce semiconductors, it is effective in reducing production cost to apply the same to a selected portion of photomasks (in about 20 to 40 plates for producing a kind of semiconductor integrated circuit devices). For example, in the semiconductor integrated circuit device referred to as a system LSI, since the gate processing step at the level of transistor devices has high density/compactness and high accuracy, and the kind of system LSIs is common for various customers, both of the usual photomasks having an opaque pattern of metal, such as Cr, or an expensive phase shift masks having durability can be used. However, in the processing of wiring layers, specifications are different for each customer, and the number of exposure steps used for the processing is small in most cases. When the photomask for KrF excimer laser lithography according to this invention is applied to such wiring steps, the production cost of the system LSI is reduced effectively. In the same manner, the half tone type phase shift mask or the Levenson-type phase shift mask according to this invention can also be used selectively for the steps to reduce the production cost of various semiconductor devices effectively.
H. As a matter of fact, the above-mentioned selective use depending on the layers to be processed is applicable not only for the various photomasks for KrF excimer laser lithography but also for the photomasks for ArF excimer laser lithography, especially for the wiring layer processing. For example, various kinds of system LSIs can be produced at a reduced cost effectively by using the mask for use in an ArF excimer laser lithography in which the opaque pattern comprises a metal film or a usual electron beam resist for the exposure up to the step of forming the gate electrode and by using the photomask for KrF excimer laser lithography according to this invention for processing upper layers.
I. It is also possible to use the Levenson-type phase shift mask with an organic polymer layer as the shade film of this invention as a photomask for use in the transistor gate electrode step instead of the exposure photomask for the ArF excimer laser lithography in which the opaque pattern comprises a metal film.
Other and further objects, features and advantages of the invention will appear more fully from the following description.